The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical multi-speed transmission uses a combination of clutches and brakes or several dog clutch/synchronizers to achieve a plurality of forward or reverse gear ratios. Typically an electronically controlled hydraulic control circuit or system uses a hydraulic fluid to actuate these torque transmitting mechanisms, as well as to lubricate and cool the transmission. The hydraulic fluid is typically stored in a fluid reservoir, or sump, located at a bottom of the transmission.
In some transmission architectures, there is a need for additional hydraulic fluid storage in a front or side cover of the transmission when the sump cannot hold all the hydraulic fluid. Typically, the sump is unable to hold the hydraulic fluid when the temperature of the hydraulic fluid increases, thereby increasing the volume required to store the hydraulic fluid. Without the additional storage capacity of the side cover, hydraulic fluid can contact moving parts, such as gear sets or torque transmitting mechanisms, and create higher spin losses which can in turn decrease fuel economy. A fluid level control valve located between the side cover and the sump controls the flow of the hydraulic fluid from the side cover to the sump. The fluid level control valve is typically fully open at low transmission operating temperatures to allow unrestricted hydraulic fluid flow from the side cover to the sump and fully closed at high transmission operating temperatures to restrict the hydraulic fluid flow from the side cover to the sump. However, pressure on the fluid level control valve due to large amounts of fluid in the side cover can force open the fluid level control valve. Accordingly, the amount of fluid within the sump can have significant variations depending on how much fluid is in the side cover. Additionally, when the transmission is operating with many shift events, hydraulic fluid from the hydraulic control system can flood the side cover, thereby increasing the amount of fluid in the side cover and increasing the pressure on the flow control valve, and again leading to unwanted variations in the amount of fluid in the sump.
Therefore, there is a need in the art for a side cover that controls the fluid flow from the side cover to the sump, eliminates dead volume in the side cover and thereby allows a constant sump volume.